Interestingly, there was one Dragon article that tried to port those rules to Al Qadim, so you might be right.I liked everything about Birthright. I liked the regency powers, realm magic, rules for domain management, ley lines, etc. Everything that is, but the boring as paste generic fantasy setting of Cerilia. If Birthright had been marketed and designed as realm domain rules for every campaign without being marketed as a setting, I think it would have done better.
(First update this afternoon, ladies and gents, sorry if I got your hopes up.)